Lyric discussion by GreenFleshyFlower 

Cover art for A Baby for Pree lyrics by Neutral Milk Hotel

I don't think it's so obvious what it's about. I think that it is about four things, the first two intertwined with each other and the second two.

Firstly, it's about a baby. If you think of Pree as a baby rather than a mother, it becomes pretty evident except for the last part of the song. I think Magnum left it ambiguous until the last part for a reason (to make the abortion part of the song more poignant).

The second part is the one already mentioned, that Pree is the mother and she is aborting her baby. That is the most obvious one.

The third is that Pree is having sex ("They'll sting through her chest with a force hard and beating/till wonderfully wet she will get until she's soaked inside her clothes"). The last part of the song mentions the consequences of her having sex.

The fourth is that Pree is being murdered. Her "babies" are her blood cells. The sorries she is sorry for are her screaming sorry to her murderer. I think this is the most emotive meaning the song can have, just by the strange juxtaposition of the song's soft melody with a murder.